Recently, data transmission that uses the Ethernet has dramatically increased. Increasingly, services of the wide-range Ethernet are widely offered since the wide-range Ethernet of SONET base utilizes a previous network. Thus, Ethernet over SONET technology with mapping of SONET data traffic is required.
FIG. 8 is a schematic structural diagram of a frame transmission system 500. In the frame transmission system 500, shown in FIG. 8, for example, a client terminal 43 of a personal computer can utilize Ethernet over SONET transmission using a long distance LAN (Local Area Network) or latter-mentioned VLAN (Virtual Local area Network Virtual LAN, Virtual LAN), and provides a ring transmission circuit 50f that comprises an optical fiber, SONET multiplex isolation devices 500a-500d that interface between each Ethernet interface and SONET interface, and LAN switches 400a-400d that correspond to the Ethernet. Further, a SONET multiplex isolation device is also called a SONET-ADM (Synchronous Optical NETwork and Add and Drop Multiplex [Synchronous Optical NETwork and Add&Drop Multiplexer]) device, ADM device, ADM or ADM node, below, without any specifically determined limits, called simply ADM node.
The transmission rate of the frame transmission system 500 is OC (Optical Carrier) 48. This OC-48 has a plurality of transmission rates OC-1, and OC-3 that are defined for North American digital hierarchy. Further, a container capacity (simply container) for transmission of information data for each transmission rate. The container capacity between the ADM node 500a and ADM node 500b that are shown in FIG. 8 are STS (Synchronous Transport Signal)—3c, the container capacity between ADM node 500a and ADM node 500c and between ADM node 500a and ADM node 500d are defined, respectively, as STS-3c ×2 and STS-1.
Thus, the Ethernet frame that is sent from server 41 is converted to a SONET frame in an ADM node 500a, the SONET frames are respectively transmitted to ADM node 500b˜ADM node 500d via ring transmission circuit 50f, then received by each client terminal 43.
Further, the frame transmission system 500 uses a UPSR (Unidirectional Path Switched Ring) for protection. This UPSR employs of a ring transmission circuit 50f switching method, and transmitting side ADM nodes 500a˜500d send identical SONET frames by 2 channels of clockwise and counter-clockwise directions of a ring transmission circuit 50f, and the receiving side ADM nodes 500a˜500d. Thus, ADM nodes 500a˜500d are switched through a path that is specified for ring transmission circuit 50f when information is detected that is commonly known as broken or deteriorated that is contained in the received SONET frame.
Then, each ADM node 500a-500d has a SONET interface part (omitted from the figures) and an Ethernet interface part. FIG. 9 is a block diagram of the Ethernet over SONET interface part during 2 switch use. The Ethernet interface part 130 that is shown in this FIG. 9 provides a 1 gigabit Ethernet card (GbE: 1 Giga Bit Ethernet Card) 10e an optical-electrical conversion part 10d that mutually converts Ethernet frame and SONET frame from this 1 gigabit Ethernet card 10e, a SONET frame, a transmission frame transmitting part 135 that sends a plurality of SONET frames by switching to 1-to-N, a 1st STS interface part 10a with mapping of N types of SONET frames that are switched for a time slot having a format of things like STS 1, a selector 10c that selects a local address SONET frame from the time slots and the frame receiving part 136 that isolates that selected SONET frames in plurality.
Thus, in the frame transmitting part 135, an input 1 Ethernet frame is switched to N SONET paths by a 1-to-N switch part 131a and STS path ID (Identification) of 1-to-N (point-to-multipoint:Point to Multipoint) is imparted by encapsulating by a plurality of multiplexing parts 117. Thus, SONET frames from the plurality of multiplexing parts 117 are output to a ring transmission circuit 50 based on STS-1 units by a 1st STS interface part 10a. 
Further, a time slot of a local ADM node address in a selector 10c of frame receiving part 136 and the SONET frame that is isolated by isolating a SONET frame of the time slot is output by this. Thus, a SONET frame format with that isolation is processed.
Previously, layer 2 switch was used for copying or isolating the transmitted frames to a plurality of Ethernet ports from 1 Ethernet port that is established for each LAN switch 400a˜400d when the LAN switches 400a˜400d output an Ethernet frame for server 41 or client terminal 43.
The L2 switch also manages the applications of the upper position layer above the data link layer that is an OSI layer, and SONET frames are transmitted that have a plurality of tags within the STS path ID when a common L2 switch is used. Also, a common LAN switch manages the layers lower than the data link layer (L2:Layer2).
This L2 switch has a bridge function and performs address learning and filtering in an L2 switch inner part by using a MAC frame MAC (media Access Control) address (Transmission origin address SA [Source Address]). The L2 switch determines whether or not the received frames are transmitted to the sending terminal of the individual ones with bridge connections when a MAC address is read out by this learning. The L2 switch confirms whether or not that MAC address is registered in an inner part MAC address table (address List) and determines things like the multicast of the received frame for the device or terminal that is affiliated with the same VLAN when this is unregistered. Further, long distance LAN is realized using SONET protocol and wide-range Ethernet can be realized.
Thus, the uses of VLAN for Ethernet over SONET are many. VLAN and common LAN both use a plurality of client terminals 43 that are physically connected. The addresses of a plurality of client terminals 43 that are physically connected in a common LAN are confirmed by L2 switch.
Previously, a plurality of user-side devices among the proposed technology used previous LAN adapters. The mutual connection via ATM networks is possible, and the network entirety which contained an ATM switch structure is made such as functioning as one VLAN.
A computer communication network has ATM switches connected to respective LAN interface adapters by interface devices and the interface applies LAN frames to transmission use by ATM networks. Thus, the user side devices can communicate with transmittable wide area networks via these LAN interfaces adapters.